1. Field of the Invention
The present invention is directed to a method of controlling a treatment process for an object in a vacuum atmosphere containing electrical chargecarriers and to a vacuum treatment apparatus. More specifically, the invention is directed to such a method or apparatus wherein at least two surfaces of electro-conductive material are exposed to the vacuum atmosphere at least one thereof being at least in part covered with material of lower electro-conductivity than the material of said one surface to form a resultant exposed surface.
The invention may be implemented for all physical vapor deposition treating processes, reactive PVD-processes as well as to all plasma-enhanced CVD-processes. It may also be implemented to other treatment processes if the two surfaces with the covering are exposed in such a process to a vacuum atmosphere with electrical chargecarriers. Such treatment processes are especially reactive or not reactive sputtering by which workpieces are sputter etched or are sputter coated and are thereby biased on predetermined electric potential or are connected to an electric reference potential or are operated on a floating electrical potential.
The present invention is also especially directed to ionplating treatment processes which are reactive or not reactive. It may also be implemented to evaporation processes, e.g. to electron beam evaporation processes, arc evaporation processes, evaporation processes with heated crucibles, all such evaporation processes being possibly part of ionplating processes. Thus, and as repeated, the invention may be implemented to all vacuum treatment processes whereat one of the electro-conductive surfaces is entirely or in part covered with a lower electro-conductive material. This may be caused by the specific treatment process itself or may be due to such a covering at such a surface already provided before the specific treatment process is started as, e.g. if such a covering is a surface oxidation of a metallic part to be exposed to the process.
2. Description of Prior Art, General
It is known that always when electro-conductive surfaces are at least in part covered by a lower electro-conductive material, called an “isolating covering” throughout the following description, and are exposed to the vacuum atmosphere containing electrical chargecarriers, a problem may arise by the fact that the isolating covering will become occupied with electrical chargecarriers. This especially if electro-magnetical force fields are applied to the vacuum atmosphere and/or inhomogeneous distributions of chargecarriers in the atmosphere lead to diffusion-forces in the vacuum atmosphere on such carriers. This may also happen at thermical CVD-treatment processes if chargecarriers are additionally used, e.g. for the activation of a surface to be treated so, e.g. ion or electron bombardment. The occupation by electrical chargecarriers leads to electrostatic charging of the isolating covering like a capacitor up to a degree where such electrostatic fields are established that an uncontrolled discharge occurs, e.g. by break-through or overflash.
Principally this problem was approached up to now in that whenever such surfaces—forming a “oneport” or single port set—were to be fed by electrical energy, as energy generators, AC-generators were applied or a DC-signal generator and additionally, simultaneously and continuously, an AC-signal generator.
In spite of the fact that the problems of uncontrolled discharges, as break-throughs and overflashings only occur stochastically distributed in time and during very short time intervals compared to the treatment process working time, one thus remedied these problems by permanently applying during the entire treatment process working time an AC-generator, be it an impulse-generator, or a RF-generator, etc.